296 



SCIENCE 



[N. S. Vol. LI. No. 1316 



whicli are to be applied during the next 

 twenty years for the encouragement of sci- 

 entific research by women in mathematical, 

 physical and natural sciences. 



Dr. G. Canby Egbinson, dean of Washing- 

 ton University Medical School, St. Louis, has 

 resigned to accept a position as dean and 

 professor of medicine in Vanderbilt Univer- 

 sity, Nashville, Tenn. 



Dr. Arthur M. Pardee, professor of chem- 

 istry at Washington and Jefferson College, 

 has been appointed professor of chemistry and 

 head of the department at the University of 

 South Dakota to take effect next September. 



The British Medical Journal states that 

 in the appointment of professors to German 

 universities precedence is at present being 

 given to university teachers who have left 

 tovms which have passed out of Germany's 

 possession. The anatomist. Professor Hugo 

 Fuchs, who had recently been appointed to 

 Konigsberg, has thus been transferred to 

 Gottingen as Merkel's successor. 



DISCUSSION AND CORRESPONDENCE 



IONIZATION AND RADIATION 



Eeoently I came across a communication 

 by Professor E. A. Houstoun^ in which it was 

 proposed to explain ionization of gases by 

 X-rays on the basis of the classical concep- 

 tion of electrodynamics, by considering the 

 intereference of spherical wavelets in which 

 the phases are distributed at random. Pro- 

 fessor Houstoun stated: 



When X-rays pass through a gas, only a very 

 small fraction of the molecules — in favorable cir- 

 cumstances, one in a billion — is ionized by them, 

 and the extent of this ionization is unaffected by 

 temperature. Writers on radiation seem to have 

 difficulty in reconciling this with the wave theory of 

 light. I venture to suggest that the difficulty 

 arises from an imperfect comprehension of what 

 the wave theory requires. 



After applying Rayleigh's solution of the 

 problem of the phases at random to ioniza- 

 tion, he arrived at the conclusion: 



1 Nature, April 24, 1919. 



Thus it is not necessary to assume that X-rays 

 consist of neutral atoms, or that the ether has a 

 fibrous structure, or to take refuge in the nebulous 

 phraseology of the quantum theory; the explana- 

 tion follows naturally from the principle of inter- 

 ference as expounded by Fresnel. 



This explanation of ionization occurred to 

 me some ten years ago but I had soon to 

 abandon it because it led to results which are 

 at variance with facts. 



Let I/r^ denote the intensity in a wavelet 

 at a distance r from the source, and n be the 

 number of wavelets coincident at that distance. 

 Then the probability of a resultant intensity 

 greater than J is given by 



Therefore if J equals the minimum intensity 

 necessary to ionize the molecules of a gas, the 

 number of molecules ionized is proportional 

 to this expression. Thus on this theory the 

 intensity of ionization of a gas falls off ex- 

 ponentially as its distance from the source 

 of X-rays is increased — a result which is con- 

 trary to the experimental fact that the in- 

 tensity of ionization varies inversely as the 

 square of the distance. 



H. M. Dadourian 

 Trinity College 



HOW DID DARWIN WORK? 



Last year Professor Francis B. Sumner 

 published a very suggestive and interesting 

 paper in The Scientific Monthly for March, 

 dealing with " Some Perils which confront us 

 as Scientists." In it he quoted with approval 

 an indignant query: " Under what project did 

 Darwin work ? " — and again, " one wonders 

 what institution or organization Newton or 

 Darwin belong to." The solitary worker of 

 Down seems the incarnation of scientific 

 genius illimainating the world with the prod- 

 ucts of its own combustion. On closer in- 

 spection, however, this conception is seen to 

 be illusory. In the whole history of science 

 there has perhaps never been a man who 

 worked more faithfully and persistently on a 

 project. It was his own project to be sure; 

 but none the less a definite project. So also, 



